Re: [GHC] #11707: Don't desugar large lists with build

15 Mar 2016

      #11707: Don't desugar large lists with build
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 I'm not as certain in the case of `rewrite`, which is a much larger
 program. This is one possibility,
 {{{#!hs
 group_rules = map parse_eqn [
               "(a * b) * c = a * (b * c)",
               "E * x = x",
                "I(x) * x = E" ]
 }}}
 Perhaps the more likely culprit is,
 {{{#!hs
 p_term = seQ q_func [p_ident, look_for '(',
                       list_of p_expr ',', look_for ')'] ## p_prim
 }}}
 where, `seQ` involves `foldr` on its list argument and was clearly
 designed expecting fusion.

 There are also a number of singleton lists, although

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11707#comment:5
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